1. Field
The present invention generally relates to mobile telephone system.
2. Description of the Related Art
More specifically, the invention relates to a method for filtering calls between a given mobile network and a mobile telephone of this network located in a determined place.
And still more specifically, the invention enables filtering the calls of a particular network at a determined place, preferably a network operating according to the GSM standard, or the UMTS standard.
The considerable boom in mobile telephones, while constituting an advantage in many respects, also entails certain drawbacks.
In particular, it would be desirable to limit, or even prohibit the communication of such equipment in certain places; for example, the case may be cited of theaters, churches, or other public or private premises wherein it is undesirable that mobile user conversations should disturb the environment.
It would thus be advantageous to enable operators running mobile networks (e.g. Itinéris—registered trademark—in France) to set up filtering for their subscribers' calls when they are in certain places.
This would, in fact, constitute an improvement in the service provided by the operator.
Broadband jamming devices are known, which can be used for neutralizing all mobile telephone communications.
But a major drawback associated with these devices is that they neutralize all the incoming and outgoing radio communications of all equipment over a very wide frequency band without distinction, and disrupt the operation of equipment having nothing to do with the mobile network whose calls it would be desirable to filter.
Moreover, regulatory constraints require certain types of calls not to be restricted, for example mobile users' calls to certain emergency services; the above-mentioned broadband jammers obviously do not observe this legal obligation.
Furthermore, jamming devices are known from FR 2 764 145 and FR 2 764 144 whose purpose is to limit the volume to be jammed by adapting the power of the jamming signal according to the volume and configuration of the space to be protected.
In these devices, the jamming signal is transmitted while sweeping the frequency ranges used by radio telephones. But such devices, which carry out jamming over all the frequencies used by radio telephones, disrupt the general operation of the network, in particular in cells located close to the area to be protected.
In addition, in this case the jamming is “brutal”, users entering the area to be protected not having the possibility of ending their communications.
A jamming device is also known from FR 2 779 610 detecting the presence of mobiles in a given area. But here again, the jamming disrupts the operation of the network and does not allow users to end their communications, which is a major drawback.